In many cases, there can be a need for a cable between a power electronic converter and an electric machine so that the length of the cable can be as much as e.g. 300 meters or even more. The power electronic converter can be for example a frequency converter and the electric machine can be for example an alternating current motor and/or generator or a transformer. The reason for the need for the long cable can be for example a lack of room for the power electronic converter in the vicinity of the electric machine and/or ambient conditions unsuitable for the power electronic converter in the vicinity of the electric machine.
An inherent inconvenience related to a long cable between a power electronic converter and an electric machine is that the control of the electric machine is more challenging than in a case where a power electronic converter in the vicinity of an electric machine. The control is more challenging because finiteness of the signal propagation speed on the cable and reflections may cause situations where instantaneous voltages and currents at the power electronic converter differ from the corresponding instantaneous voltages and currents at the electric machine. A further inconvenience related to a long cable is that voltage reflections may cause over-voltages at the electric machine. In a disadvantageous case, the reflection-based over-voltages may damage the insulations of the electric machine. A traditional approach for reducing the reflection-based over-voltages is to set a lower limit to the temporal widths of voltage pulses produced by the power electronic converter. An inconvenience related to this approach is that the lower limit has to be sufficiently long, i.e. to include a sufficient safety margin, in order to achieve an acceptable operation in different situations. Therefore, in some cases, the application of the lower limit may unnecessarily degrade the quality of the control.